Made sure FilterEngine instances are always initialized

src/FilterEngine.cpp

Index: src/FilterEngine.cpp
===================================================================
--- a/src/FilterEngine.cpp
+++ b/src/FilterEngine.cpp
@@ -16,16 +16,17 @@
  */
 
 #include <algorithm>
 #include <cctype>
 #include <functional>
 #include <string>
 
 #include <AdblockPlus.h>
+#include "Thread.h"
 
 using namespace AdblockPlus;
 
 extern std::string jsSources[];
 
 Filter::Filter(JsValuePtr value)
     : JsValue(value)
 {
@@ -127,25 +128,32 @@ bool Subscription::IsUpdating()
   return result->AsBool();
 }
 
 bool Subscription::operator==(const Subscription& subscription) const
 {
   return GetProperty("url")->AsString() == subscription.GetProperty("url")->AsString();
 }
 
-FilterEngine::FilterEngine(JsEnginePtr jsEngine) : jsEngine(jsEngine)
+FilterEngine::FilterEngine(JsEnginePtr jsEngine)
+    : jsEngine(jsEngine), initialized(false)
 {
+  jsEngine->SetEventCallback("init", std::tr1::bind(&FilterEngine::InitDone, this));
   for (int i = 0; !jsSources[i].empty(); i += 2)
     jsEngine->Evaluate(jsSources[i + 1], jsSources[i]);
+
+  // TODO: This should really be implemented via a conditional variable
+  while (!initialized)
+    ::Sleep(10);
 }
 
-bool FilterEngine::IsInitialized() const
+void FilterEngine::InitDone()
 {
-  return jsEngine->Evaluate("_abpInitialized")->AsBool();
+  jsEngine->RemoveEventCallback("init");
+  initialized = true;
 }
 
 FilterPtr FilterEngine::GetFilter(const std::string& text)
 {
   JsValuePtr func = jsEngine->Evaluate("API.getFilterFromText");
   JsValueList params;
   params.push_back(jsEngine->NewValue(text));
   return FilterPtr(new Filter(func->Call(params)));